It's not 5 years behind, engine tech is more on a ~15 year cycle, or even more. CFM LEAP, latest short-to-medium-haul airliner engine from CFM (GE+Safran) is f

It's not 5 years behind, engine tech is more on a ~15 year cycle, or even more. CFM LEAP, latest short-to-medium-haul airliner engine from CFM (GE+Safran) is from 2013 (first run). Its predecessor, CFM56, is from 1974 (first run) and saw a few evolutions, including as late as 2009.